Quantitative proteomic profiling of matched normal and tumor breast tissues

Proteomic analysis of breast cancer tissue has proven difficult due to its inherent histological complexity. This pilot study presents preliminary evidence for the ability to differentiate adenoma and invasive carcinoma by measuring changes in proteomic profile of matched normal and disease tissues. A dual lysis buffer method was used to maximize protein extraction from each biopsy, proteins digested with trypsin, and the resulting peptides iTRAQ labeled. After combining, the peptide mixtures they were separated using preparative IEF followed by RP nanoHPLC. Following MALDI MS/MS and database searching, identified proteins were combined into a nonredundant list of 481 proteins with associated normal/tumor iTRAQ ratios for each patient. Proteins were categorized by location as blood, extracellular, and cellular, and the iTRAQ ratios were normalized to enable comparison between patients. Of those proteins significantly changed (upper or lower quartile) between matched normal and disease tissues, those from two invasive carcinoma patients had >50% in common with each other but <22% in common with an adenoma patient. In invasive carcinoma patients, several cellular and extracellular proteins that were significantly increased (Periostin, Small breast epithelial mucin) or decreased (Kinectin) have previously been associated with breast cancer, thereby supporting this approach for a larger disease-stage characterization effort.